const mongoose = require('mongoose')
const schema = new mongoose.Schema({
  title: {
    type: String
  },
  parent: {
    type: mongoose.SchemaTypes.ObjectId, ref: 'Category'
  }
})

schema.virtual('children',{
  localField:'_id',
  foreignField:'parent',
  justOne:false,
  ref:'Category'
})
schema.virtual('newsList', {
  localField: '_id',
  foreignField: 'categories',
  justOne: false,
  ref: 'Article'
})

module.exports = mongoose.model('Category',schema,'categories')